The present invention relates generally to an electromechanical system for continuously infusing medication into a patient and, more particularly, to a fluid delivery control and monitoring apparatus used in such a medication infusion system.
Until recently there were two major techniques available for delivering drugs to a patient when the drugs cannot be orally administered. The first technique is to inject the drug into the patient with a syringe and needle to deliver an appreciable dose at relatively infrequent intervals. This technique is not always satisfactory, particularly when the drug being injected is potentially lethal, possibly has undesirable side effects when given in a large dosage, or must be delivered more or less continuously to arrive at a desired therapeutic result. This technique leaves much to be desired. The risks of overdosage or harmful side effects may be reduced by giving smaller injections at more frequent intervals, an inconvenient and not altogether satisfactory alternative.
The need for delivering a drug more or less continuously to achieve a desired therapeutic effect gives rise to the second technique, which involves a continuous delivery of medication to the patient, typically through an intravenous drip. Medication may also be administered using an intravenous system with an injection into a complicated and cumbersome interconnection of IV tubes, hoses, and other components. Drop counters are used to measure the amount of fluid delivered, and medications are often delivered in a large dose through injection into the IV lines, with the medication being somewhat diluted by the fluid.
A relatively recent alternative to these two techniques of administering medication to a patient is the medication infusion pump. A valuable and much needed development, the medication infusion pump can be used to administer drugs to a patient in small, carefully measured doses at frequent intervals or, with some devices, slowly but uninterruptedly. A therapeutic regimen with an infusion pump can be controlled electronically to administer precisely measured quantities of a drug at precisely planned intervals to give a gradual infusion of medication into the patient. The infusion pump makes possible a closer approximation to the natural maintenance of biochemical balances in the body because of its operation in a repetitive small dose.
Disposability is an important consideration in the design of medication infusion systems. Parts of the system through which medication is pumped must be sterile, so that in most applications some of the equipment is used and then discarded. The disposable parts are typically replaced at regular intervals, typically on a daily basis. Disposability of the fluid pump portion of the infusion device is a highly desirable feature. It would be very convenient to design a fluid pump in the form of an attachable cassette of economical design which could easily be installed onto a main pumping unit. A cassette which uses a small number of parts, is easily mass producible, and is capable of delivering liquid medication or other therapeutic fluids with a high degree of precision is described in U.S. patent application Ser. No. 07/127,333 now 4,872,813 issued on Oct. 10, 1989, entitled "Disposable Cassette for a Medication Infusion System." The contents of that application are incorporated herein by reference.
The disposable cassette which is referred to above includes a fluid pump affording a high degree of accuracy in fluid delivery, with the degree of accuracy being maintained throughout the life of the product. The cassette also provides means for conveniently and easily priming the pump, and includes a bubble trap to prevent the frequent shutdowns and alarms which are a problem with presently available pumps. The cassette also includes additional devices such as pressure sensing means and bubble detecting means which in conventional medication infusion systems constitute separate assemblies.
A fluid monitoring and control system for use with disposable cassettes is needed to ensure accurate and safe delivery of therapeutic fluids. The design of such a system requires careful attention to factors involved in the accuracy of fluid delivery, and instrument monitoring functions are necessary to insure safe operation of the system.
There has been a long-felt but unresolved need for the development of a medication infusion management system that can be used for patient care in both hospitals and home health care applications. A desirable system would provide a reliable and improved product for current applications to encourage the use of new therapeutic techniques, reduce the cost of hospitalization by improving care and decreasing labor and inventory costs, and would be versatile enough to allow intra-arterial and subcutaneous infusions. Primary requirements of such a system would be volumetric accuracy, state-of-the-art safety functions, and a capacity for independently controlling more than one pumping channel, each with a separate line to the patient.
Ideally the pump of the medication infusion system would be substantially smaller and lighter than current hospital pumps while at the same time incorporating multiple pumping channels. Together with the possibility of extended battery-powered operation, these features would make a device that is very well suited to ambulatory care, intensive care, emergency transport, emergency care, and operating room use.
A system with the capacity for multiple pumping channels, a variety of disposable configurations, and a library of software functions could combine the capabilities of several currently available devices into one single unit. For example, the need in a hospital for separate syringe pumps, PCA pumps, neonatal pumps, general purpose pumps, and computer communications pumps could be eliminated in favor of one system that could satisfy the requirements for all these devices.
The necessity for cost containment is recognized in the health care industry. Costs can be broken up into three categories: material, labor, and maintenance. With intravenous infusion devices, a major consideration is the cost of disposables, since a large number are required per year. A medication infusion system that keeps down the cost of disposables, is easy to set up, simple to use, and highly reliable would be a great boon to the health care field.